|"Is this all real? Or has this been happening inside my head?"
The topic of this article is of a real-life subject that has been mentioned "in-universe" in a canon source. The Harry Potter Wiki is written from the perspective that all information presented in canon is true (e.g., Hogwarts really exists), and, as such, details contained in this article may differ from real world facts.
Sir Winston Leonard Spencer-Churchill (30 November, 1874 – 24 January, 1965) was the Muggle Prime Minister from 10 May, 1940 to 26 July, 1945 and again from 26 October, 1951 to 6 April, 1955. Churchill was widely regarded as one of the greatest wartime leaders, due to Britain's involvement in the Second World War.
Winston Churchill enjoyed a good working relationship with the Minister for Magic, Leonard Spencer-Moon, as they oversaw a period of great international turmoil in both the wizarding (global wizarding war) and the Muggle world (Second World War).